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Measurement of ANSI for CRT & DLP/LCD?

Discussion in 'Projectors, Screens & Video Processors' started by Paulherb, Jan 25, 2002.

  1. Paulherb

    Paulherb
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    I know that DLP/LCD & CRT are quite different beasts in how they produce a picture.

    My question is how many ANSI on a CRT(roughly) equals ANSI on a DLP/LCD to give the same brightness of picture?

    Any help would be most welcome!


    Cheers


    Paulh.
     
  2. Roland @ B4

    Roland @ B4
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    This one come up every so often.

    When LCD projectors were firts introduced there were huge wars as to who had the brightest projector. (one manufacuter quoted their light out put without the LCD pannels in) In the end the American National stadards Institiute (ANSI) steped in with a scheme that each manufacteur thought was reasonable and easy to recreate. CRT projector wer never intended to be include in this equation but had to conform anyway. Basiclly a projector is setup correctly for picture rendition contrast bightness etc useing approved test patterns. then a full white field is shown and nine zones measured on the screen. the nine values are then averaged out and you get your lumen reading.

    Projectors with Lamps in (LCD, DLP) are very good at produceing bright images because their technology requires a block to be put in the way to create black. a typical domestic LCD is about 800 ansi lumens.

    CRT on the other hand is not so clever at producing full white fields. It has a device called a beam current limiter which effectivly stops the amount of power that can be written to the screen at anyone time or it would either blow up or burn a whole in it. However CRTs are very good at producing peak whites ie small areas of bright lights in an average video picture. In fact an average video picture has between 10 and 15% peak whites.
    A typical CRT is about 180 ansi lumens. So from the specifications about a quater the brightness.

    However
    When you measure your 180 ANSI lumen projector on a 10% peak white field it is able to produce 1200 lumens because the beam current limmiter has not yet cut in.

    Your average CRT projector properly set up against your average properly set domestic LCD procector will have darker blacks, brighter whites, better colour saturation, higher contrast range,smoother............ yes and be the twice size of the box the other other one shipped in.

    Specifications mean every thing to the magazines. Very often they mean nothing to the sound or picture quality.
     

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